Still waiting for phone

Everytime someone phones me but thats where it stays.i am fed up its the second timw my new phone is in for repairs the second time i booked it in on the 8 and its still at the advance repair shop still dont know whata wrong with it.it was a giftfor christmas so now i wont have a gift.this is really bad service and now i read that i have the right up to 6 months to demand a new phone.i want this sorted out